Laminated spinneret and process for making



Dec.

D. R. HULL LAMINATED SPINNERET AND PROCESS FOR MAKING Filed April 10. 1952 IN V EN TOR:

Donald RJhLZL 71; arm

A TTORNE Y United States Patent LAMINATED SPINNERET AND PROCESS FOR MAKING Donald R. Hull, Seaford, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Apr. 10, 1952, Ser. No. 281,567

8 Claims. (Cl. 18-8) The present invention relates to spinnerets useful in the production of filaments by dry, wet, or melt spinning procedures and to a process for producing these spinnerets.

In the latest methods for spinning filaments and fibers, particularly by the melt spinning and dry spinning methods whereby filter packs of considerable density are employed before the spinneret, it is necessary to have the spinneret made of a load-bearing metal of a sufiicient thickness to withstand considerable pressures without deformation. Consequently, the older methods of making spinnerets from thin metal blanks, by simply punching out the extremely small diameter orifices desired, or by drilling with extremely fine drills alone, are no longer applicable.

Methods which have been developed in response to the new requirements possess certain inherent deficiencies. These methods generally involve removing part of the metal where the orifice is to be and thereby reducing the thickness of the spinneret blank at that point to a thinness that can be punched or drilled to give the small diameter orifice in common usage. Such techniques, as counterboring with a conical bit or by drilling step-wise with progressively smaller bits or by drilling with one larger bit to reduce the thickness of the spinneret blank at the point in question and then making the small diameter orifice, all suffer from the requirement that these counterbores must be sufiiciently large to admit the bit holder or shank, or the punch holder or shank to the bottom of the bore in order to produce the small diameter orifice. On the other hand, the size of this counterbore cannot be made so large as to seriously reduce the loadbearing strength of the spinneret.

In addition, it is necessary to smooth the bores of these drilled holes as well as the conical sections by a coining or polishing operation. It is further necessary to maintain the lengths and diameters of the small orifices to within the precise tolerances of :0.0001 or better, particularly when the orifices are smaller than 0.005 in diameter. As a consequence of the special tools and skills required, the production of spinnerets having small diameter orifices by these methods is an involved and expensive procedure. Any slip in the production of any single orifice spoils the Whole spinneret, since damageto these small diameter orifices is not usually repairable. A similar condition exists in the spinning step, and in the spinneret handling operations auxiliary thereto, in that any damage to a single orifice has required the rejection of the whole spinneret with its resultant economic loss.

It is an object of this invention to provide a laminated spinneret containing a multiplicity of small diameter orifices, Which will support a pressure load of considerable magnitude and is relatively inexpensive to manufacture. It is a further object of this invention to provide a process for efficiently and economically producing such a spinneret. It is a still further object of this invention to provide a spinneret, useful in the spinning of filaments under considerable pressure, which can readily be repaired when damage is done to the fine diameter orifices. Still another object of this invention is to prefabricate the components of the spinneret and then to assemble them in a suitable manner into the useful article. Other objects will appear hereinafter The objects of this invention are accomplished by drilling or punching spinneret orifices in a face portion of relatively thin metal, e.g., a foil, drilling larger diameter holes in matching pattern in a relatively thick spinneret blank of suitable dimensions to form a backing for the face, and then bonding the relatively thin face portion to the relatively thick backing member, so that the orifices of the face are in substantially coaxial alignment with the larger diameter holes in the backing member, to form a composite or laminated spinneret suitable for use in the spinning of filaments.

In the drawings, which illustrate preferred embodiments of the invention,

Figure 1 is a cutaway face view of one embodiment of spinneret,

Figure 2 is a sectional view taken on the line 22 of Figure 1,

Figure 3, is a perspective view of the component parts of the spinneret before bonding together to make the spinneret shown in Figure l, and

Figure 4 is a perspective view of the component parts of another embodiment of spinneret.

Referring to Figures 1 to 3, in a 2-inch diameter disk 10, suitably of carbon steel and -inch thick, are drilled five inch diameter holes 11, equally spaced and concentric With the perimeter of the disk on the circumference of a 1 inch circle. Holes 12 having a diameter of 0.010 inch are punched in a similar pattern in a 0.008- inch stainless steel wafer 13, which had been preplated with a 0.0001-inch layer of copper on one face only. After thorough cleansing, the wafer is assembled with the copper-plated side in contact with the carbon steel disk in a clamping fixture so that the small diameter orifices and the A inch diameter holes are coaxially aligned. Heating the assembly in an atmosphere of hydrogen for one hour at 1120 C., with pressure exerted to hold the stainless steel wafer firmly against the disk, produced a Well-bonded spinneret as shown in Figures 1 and 2.

This method of making spinnerets is even more valuable With the large spinnerets which contain a large number of orifices for spinning staple yarns. This large number of orifices in a given spinneret blank increases the probability that any given spinneret blank will be rejected for damage to one or more orifices during the manufacturing operations of the prior art. The method of manufacture of this invention reduces that possibility. Furthermore, the large diameter spinnerets required for spinning staple yarns must be made unduly thick when using the prior methods of drilling of so many, weakening counterbores large enough to admit the tool holder or v cated generally by 16, with the parallel rows being 7 inch apart and the chords subtending arcs of a three-inch diameter circle concentric with the circumference of the spinneret blank. In the chordal rows the holes are spaced inch apart. From a roll of stainless steel foil 0.015.

inch thick and A inch wide, which had been prepunched with 0.015-inch holes 17 on the center line of the 7 inch strip at intervals, are cut strips 18 of suitable dimensions to lay across the spinneret blank in alignment with the predrilled .chordally arranged holes. The predrilled spinneret blank is plated with 0.0001-inch of copper and the clean inch strips of prepunched stainless steel foil are placed on the spinneret blank with the 0.015- inch diameter orifices coaxially in alignment with the ,4 inch holes. This assembly is next clamped in a suitable device to maintain a positive pressure on the strips while holding them in place against the spinneret blank and is heated in an atmosphere of hydrogen for one hour at 1120 C. After cooling, the spinneret is ready for use.

The above procedure was repeated except that, instead of plating the spinneret blank with copper, it was plated with 0.0001 inch of silver. Because of the lower melting point of silver it was necessary to heat the assembled blank and foil strips to a temperature of only 1000 C., in an atmosphere of hydrogen, to obtain acceptable bonding.

The temperatures given for the brazing procedures in the above illustrations are not meant to be limitative. It is, of course, necessary to employ a temperature above the melting point of the brazing metal and below the deformation temperature of either the foil or the spinneret blank. Where steel or iron is used, the temperature may not exceed 1535 C. and preferably will not exceed 1400 C. The brazing temperature, although higher than the melting point of the brazing metal, should not be high enough to vaporize the brazing metal into the orifices.

It is to be understood that the process of this invention is not limited to the bonding method described, involving copper brazing or silver brazing by means of a plated layer 0.0001 inch thick on one member. Other thicknesses of copper or silver may be used, for example, from 0.00005 to 0.0005 inch thick, the criterion being that sufficient brazing metal be present to effect an adequate bond without there being an excess to flow into and obstruct the small diameter orifices in the metal foil.

As demonstrated in the above illustrations, it is possible to put the brazing metal on either the thin metal foil or on the thick spinneret blank. It is equally possible to put a thin layer of brazing metal on both as long as the total thickness of brazing metal falls within the above specified limits. Other suitable variations of the bonding method will be apparent to one familiar with methods used for bonding metals. Aluminum or silver-copper alloy brazing may be advantageous instead of the copper or silver brazing method described above. Furthermore, such methods as spot welding or resistance welding may sometimes be desirable, particularly when the thin metal foil is in one piece and covers the whole spinneret as in Figures 1 and 2.

An important advantage of this invention is that it permits repair of holes damaged in handling, whereas it was previously necessary to discard the spinneret. The method for repairing these spinnerets simply involves removing the narrow strip in which the damaged hole exists by localized heating, followed by rebonding a new narrow strip in its place by the same method as described above. Such strips need not be the inch width given in the examples, but can be of any convenient width for a given spacing of the orifices in the spinneret blank.

Should any orifice be formed imperfectly in the succession of orifices on the narrow strip of thin metal foil, it is possible, by judicious cutting of the imperfect strip, to Waste only the imperfect hole (in chordal rows of holes the number of holes varies from row to row). Even with an inexperienced operator, only a few perfect orifices on one side of the imperfect orifices need be wasted.

A process of spinneret manufacture has been illustrated above wherein small orifices were prepunched in a thin metal disk the size of the spinneret or wherein small orifices were prepunched in narrow strips to fit over the rows of holes in the spinneret blank. Obviously, the process of this invention is not limited to these embodi ments, but includes such variations as prepunching or drilling a small orifice in a small square, oval, or circular piece of thin metal, which can then be brazed over each hole individually in the spinneret blank. Likewise, if the hole pattern in the spinneret is composed of holes arranged in concentric circles, the thin prepunched foils can be in the form of annular rings. The contour of the orifice in the thin metal laminate may correspond to any disclosed in the prior art.

Another important advantage of this method of spin neret manufacture is that it lends itself particularly well to the production of spinnerets having orifices of noncircular cross section. These non-circular cross section orifices, for example, crescents, triangles or crosses, may be readily punched into the thin metal foil which is then bonded to the spinneret blank as described hereinabove. Another advantage is that the perfection of each and every individual small diameter orifice, whether circular or non-circular in cross section, may be precisely determined by a close examination of both sides of the thin metal foil before it is bonded to the spinneret blank.

It is likewise to be understood that the metal foil em ployed in this invention may be any of a wide variety of stainless steel alloys, or may equally well be carbon steel, a noble metal or other suitable metals and alloys. Preferably, the foils are made of stainless steel alloys which are hard, tough and resistant to heat, oxidation and corrosion. The foil thickness will be preferably in the range of from 0.005-incl1 up to 0.040-inch, but can be either thicker or thinner. The spinneret blank may be carbon steel, stainless steel, or any of the many ferroalloys or other suitable non-ferrous metals readily avail able in the trade. The thickness of this blank may vary from /8 inch up to 1 inch or even more, depending on its diameter. Usually its thickness will be within the limits of from to /8 of an inch. The drilled holes are preferably of the smallest diameter than can be drilled conveniently in the spinneret blank of the thickness used. These holes may vary from A to /4 inch, but will usually be within the range of A to A; of an inch. The small diameter orifices in the metal foil may vary in diameter from a few ten thousandths to a few hundredths of an inch, depending upon whether they are to be used in the dry spinning art, melt spinning art or the wet spinning art.

For the purposes of this invention, the surfaces of the spinneret blank and the thin metal foil should be sufficiently smooth and flat to obtain adequate bonding between them in the brazing operation.

It is seen that this method of manufacturing spinnerets permits a substantial saving of the more expensive and sometimes difficultly procurable stainless steel alloys, by using them only in the thin metal foil. By using a metal such as carbon steel, copper, aluminum, or the like, for the thick spinneret blank, a further advantage is achieved in that the spinneret has greater temperature uniformity across its face because of the superior heat conductivity of these metals as compared to stainless steel.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

What is claimed is:

1. In a spinneret assembly, a laminated spinneret comprising a face portion of relatively thin metal bonded to and supported over substantially its entire area by a backing member of relatively thick metal, the face and backing members being bonded together by fused metal, said face portion being provided with spinning orifices and said backing member being provided with holes larger than said orifices and in substantially coaxial alignment with said orifices, said face portion being made up of a plurality of strips bonded side-by-side to the backing member.

2. A spinneret as defined in claim 1 wherein said face portion is composed of stainless steel alloy foil from 0.005 up to 0.040 inch thick.

3. A spinneret as defined in claim 1 wherein said backing member is a steel disk from Ms up to 1 inch in thickness.

4. A spinneret as defined in claim 1 wherein the holes in said backing member are from to /4 inch in diameter.

5. A method of making a spinneret which comprises punching spinneret orifices in a relatively thin steel wafer preplated on one face with a layer of copper 0.00005 to 0.0005 inch thick, drilling larger holes in a matching pattern in a relatively thick steel disk, clamping the disk to the copper face of the wafer with the holes in substantially coaxial alignment with the orifices in the wafer, and heating the assembly in a hydrogen atmosphere to a temperature between the melting point of the copper and the deformation temperatures of the wafer and disk to bond the assembly.

6. A method of making a spinneret which comprises drilling a pattern of holes in a steel spinneret blank, plating the blank with a layer of brazing metal 0.00005 to 0.0005 inch thick, laying strips of steel foil repunched with spinneret orifices in a matching pattern over the holes of the blank so that the orifices are in substantially coaxial alignment with the holes in the blank, and heating the assembly to bond the strips to the blank.

7. A method as defined in claim 6 in which the brazing metal is copper and the assembly is heated to a temperature above the melting point of the copper and below the deformation temperature of the assembly in an atmosphere of hydrogen.

8. A method as defined in claim 6 in which the brazing metal is silver and the assembly is heated to a temperature of about 1000 to 1400 C. in an atmosphere of hydrogen.

References Cited in the file of this patent UNITED STATES PATENTS 1,337,258 Ohlson Apr. 20, 1920 1,366,166 Criggal Jan. 18, 1921 1,492,594 Dreyfus et al. May 6, 1924 2,140,806 Marsh Dec. 20, 1938 2,211,946 Graves Aug. 20, 1940 2,341,555 Jones Feb. 15, 1944 2,461,640 Hallberg Feb. 15, 1949 622,258 Vltavsky Apr. 28, 1949 FOREIGN PATENTS 442,783 France Sept. 9, 1912 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N0 2,965,924 December 27 1960 Donald Re Hull It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below'.

Column 3, line 3, after "3/16" insert inch line 70, for "orifices" read orifice column 4, line 3, for "variations" read variation line 39, for "than" read that column 5, line 26, for "repunched" read prepunohed Signed and sealed this 13th day of June 196i,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

